Radio relaying system



New. 8, 1949 BEVERAGE 2,487,513

RADIO RELAYING SYSTEM Filed Oct. 26, 1945 Fig 1.

FRO/7 77/5 WEST 195 Cf VE/ IN VEN TOR.

H rold H. Bel/e rage ATTOB/VEK ther of two terminals troubles due to thequencies in different relay chain.

clude the following transmitting intelligence nals associated with shallbe free from Patented Nov. 8, 1949 Harold H.

Delaware Application October 26, 1943,

Beverage, Riverhead, Radio Corporation of America,

N. Y., assignor to a corporation of Serial No. 507,696

- 8 Claims. (Cl. 250- 15) This invention relates to radio relay systemsand. is particularly concerned with methods and apparatus forcontrolling relay stations from eiwhile avoiding feedback use of thesame carrier frelinks of transmission in a Where unmanned relay stationsare used in an ultra-high frequency communications system,

.feedback difficulties would Occur if the repeating frequency were toreach a remote transmitter having the same or a frequency with which itwould cause undesirable heterodyning.

The advantages of using unmanned relay stations in an ultra-highfrequency network are well known. Much thought has been directed to thesolution of problems relating to radio relaying.

The improvements covered by my invention are set forth withparticularity in the appended claims. The objects of the inventionitself inas well as others which will be apparent in view of thesubsequent detailed description. y A principal object is to provide arelay system using a minimum of equipment and a minimum number offrequencies.

It is a further object to provide a system for through a chain oiunmanned relay stations from either of two termisaid chain.

It is still another object of my invention to provide lock-out meanswhereby unmanned relay stations when selected for repeatingcommunications from either of two-terminal stations shall not be subjectto control by the other terminal station until released.

Again, it is an object to provide a relay system in which the carrierfrequencies chosen for linkby-link transmission in a given chain ofrelays feedback troubles In the description to follow, reference is made:to the accompanying drawings, in which: I

Fig. 1 shows schematically an arrangement of terminal and relaystations, the system being such that a pair of receivers, each operableto receive from a different direction is connected to 9. commontransmitter having a two-directional antenna system;

Fig. 2 shows more ment which I preferably in detail a circuit arrangeuseat an unmanned repeating station for selective control thereof iromavoid feedback and west station or at relay having an E-shaped core issubstituted for two independent relays 44 and 45 in Fig. 2.

In some of the known relay systems, communications are possible inbothdirections simultaneously. Such systems require a considerable number ofcarrier frequency assignments'in order to "interference singing. In mypreferred arrangement feedback is avoided by allocating frequencies totransmitting and receiving equipment at a given repeating station whichdo not interfere with one another and do not reach to any otherrepeating station where the same frequencies are used for transmission.

In Fig. 1, the subscripts applied to letters T (for transmitter) and R(for receiver) represent different carrier frequency assignments. Thefrequencies assigned to the various radio links in the system arerepresented by wavelength legends the character M represents theoperating wavelength on which the transmitter at the west terminaloperates and represents the same frequency as that to which the receiverR1 at relay station A is tuned. Transmitter T2 at relay station A uses acarrier frequency represented by the character is to which receivers R2both at the west station and at relay station E are receptive.

Following through the frequency assignments of the remainder of therelay chain, it will be observed that'transmitter T3 at station Boperates on a wavelength M to which receivers Rs at both relay station Aand relay station C are receptive.

"Transmitter T1 at station C communicates with length 7&3 sent out bytransmitter T3 at the east terminal. I

In order to avoid feedback dilnculties, it is to be understood thatstation C is located sufficiently remote from the west terminal so that,despite a common frequency assignment, the two transmittel-s T1 aresubstantially non-interfering. Assume, for example, the effective reachof the signals is 30 miles and that the adjacent stations are 30 milesapart. will be located 66 miles away from the receiver R2 Then thereceiver R2 at station B at the west terminal. Both of these receiversare responsive to the-carrier. is, of transmitter T2 at station A, butwithin the 30-mile radius or station A, no interfering carriers are usedeither at the station B. Furthermore, any two transmitters which havethe same. wavelength assignment are located at least 90 miles apart, asbetween station A and station D, where the wavelength assignments, A2 oftransmitters T2. are the same. Accordingly, my system provides a highdegree of freedom from acoustic coupling, termed singing, and otherundesirable heterodyning.

As a practical matter, it i found that most of the required relaying ofcommunications by networks of the class described is in one directiononly and it is only occasionally that it is desired to relay in theopposite direction. By taking advantage of this fact, a reversibleone-way repeater system may be used requiring a minimum number offrequencies. Furthermore, as a practical matter, it becomes unnecessaryfor one-way reversible systems to duplicate the transmitter equipment atthe several unmanned repeater Sta-- tions. Transmitters havingbi-directional antenna systems are well known in the art and the use ofsuch antenna systems is contemplated in carrying out my invention.

Referring now to Fig. 2, I shown therein a circuit arrangement which,although capable of modification in various ways, is suitable for remotecontrol of an unmanned repeater station. The receivers R1 and R3 may beconsidered as differently tuned to signals derived from stations to thewest and east, respectively. The transmitter T2 radiates towardsstations both to the east and to the west and has assigned thereto acarrier frequency which is shared only by other trans mitters T2 whichare sufliciently remote to cause no interference.

Each of the receivers R1 and R3 is arranged to actuate an electronicrelay 4| and 42 respectively whenever a response is made to a carrierwave to which the individual receiver is tuned. Electronic relays arewell known in the art and any one of a number of different types'of suchrelays may be chosen for use in the present invention. Preferably such arelay is made responsive to carrier currents, whether modulated orumnodulated. A so-called squelch relay may be used if desired. In thiscase the incoming carrier wave is rectified and produces a biaspotential to be applied to a normally blocked amplifier tube.

When the tube is unblocked it closes a circuit path for operating anelectromagnetic relay.

Grid-controlled tubes Whether of vacuum or gaseous discharge type may beused, depending upon the amount of power which is to be switched on andon". The circuit to be switched by relay 4| may be traced from a sourceof direct current 43 through the winding of an electromagnetic relay 44and thence through normally closed contacts 46 of relay 45, and throughconductor 41 and the space path (not shown) of the electronic relay 4|to ground.v

The circuit controlled by electronic relay 42 may be traced from source43 through the winding of relay 45, through the normally closed contacts48 of relay 44 and thence through conductor 49 and the space path ofelectronic relay 42 to I ground.

The purpose of contacts 46 and 48 is to lock out the operation of one ofthe relays 44, 45, after the other one has taken control. Theun-operated relay must be rendered incapable of upsetting the stationcontrol conditions as established by signals first arriving at therepeater station from either terminal. Thus, when relay 44 is actuated,receiver R1 which receives signals from the west is connected to thetransmitter T2 and relay having three the modulator of this transmitteris thereupon rendered subject to control only by signals originating atthe west terminal. Likewise, when relay is actuated in response to acontrol carrier wave received on receiver R3, the intelligence by whichthis carrier wave may be modulated is applied to the modulator oftransmitter T2 so as to repeat the signals to a succeeding stationfurther to the west.

Means for applying the traffic signals to transmitter T2 from one or theother of the receivers R1 and R3 will now be described:

The detected signals which are impressed upon the output circuit ofreceiver R1 may be switched into the input circuit of the modulator intransmitter T2 by energizing coil 50 in a polarized relay so as to throwits armature 5| against contact 20. This establishes the desiredconnection between the output circuit of receiver R1 and the input totransmitter T2. Coil 50 of the polarized relay is .energized by theclosure of contacts 52 on relay 44. This contact closure connects source43 through coil 50 and thence through the winding of a relay 53 toground. When relay 53 is energized, the pulling up of its armature 54connects the positive terminal of a power supply (so labelled) to thetube equipment in the transmitter T2 whereby this transmitter is enabledto radiate a modulated carrier wave.

If reception is first obtained at a given repeater station from a pointto the east thereof, then the detected traflic signals received onreceiver R3 are applied to the modulator of transmitter T2 by throwingthe armature 5| on the polarized relay against contact e. This isaccomplished by energizing the coil 55 of this relay. The energizingcircuit may be traced from source 43 through contacts 56 of relay 45,the coil 55 and thence through the winding of relay 53 to ground.

It will be apparent that the power supply is fed to the transmitter T2byenergizlng relay 53 regardless of the source of the signals, or theparticular receiver R1, R3 which is for the time being responsive. It isalso apparent that once the transmitter T2 is associated with a givenone of the receivers R1, R3 for reception from a particular terminal, nointerference is possible as a result of receiving signals from the otherterminal.

It is true that both receivers R1 and Rs may be allowed to remain in astandby condition in readiness for reception of any signals to whichthey are respectively tuned, but the tongue 5| of the polarized relayconnects the transmitter T2 to only one of the receivers at a time.Furthermore, only one of the remote control relays 44, 45 is operable atanyone time, due to the fact that each of the windings of these relaysis in circuit with break-contacts of the other relay. Reversal of fore,possible only after release and de-energizing of the relay which wasfirst actuated.

' A modification of my invention is shown in Fig. 3 wherein it isapparent that the contacts 46, 48, 52, and 56 may be operated by meansof a single positions. Such relays are well known in the art and areusually'so constructed that one winding draws the movable contactsagainst stationary contacts on one side, whereas another winding drawsthe movable contacts into engagement with stationary contacts on the Ina neutral position, the normally 52 ant 56 are open with respect to bothsides and the normally closed contacts 46 "and 48 remain normally closeduntil one or anather of the two coils l4, finisienergizedficirruitconnections are not shown in Fig, 3, since theyJmay be-thesame asinFig..2,

Itrwill beapparent to those skilled, in the art that my improvements inradio relay Systems are to be found useful regardless of'the form ofintelligence which is transmitted by .way of trafiic signals. Thus thesystem may be used forpointto-point communications, for broadcastingofentertainment, whether by. frequency-modulation oramplitude-modulation waves, and alsofor, television and facsimiletransmissions: v Itshouldbe; clearly understood that the illustration ofFigure l.is given only by way of example and that a lesser or greaternumber of relay stations may be used as required .by thedistanceseparating the west and the east terminal sta- Itions. The onlyrequirement isthat the. terminal stations .each have a transmitter andreceiver adapted to operate with one of. thejreceivers and transmittersrespectively, of the next, adjacent relay station.

. If the distance between the, two terminal stations is so shortthatonly one intermediate relay .station would be required, it isapparent that the technique of relaying as hereinbefore described -may,nevertheless, be followed. without modification. Referring again .toFig. 1,- it will-be seen that stations A and D utilize thesamecombination. of frequencies in their respective receivers andtransmitters Accordingly, proximity permits, station .A may be situatedapproximately halfway between the-west andeast terminals and a two-waycommunicationsystem'would be provided, subject", however, to thecondition that the transmitter T2 at the repeater station would bealternatively controlled by its two associated receivers.Suchalternative control would be-sub- .ject to the transmitting timesindividually appropriated by the west and east transmitters; .'As soonas either terminal transmitter ceases to radiate, the remote controlrelays of the repeater station are restored to-normal and are madesubject toreversal of the relaying direction ,by an incoming signal fromthe opposite terminal.

For other numbers of relaystations the operating frequencies of thetransmitter and receiver at the east terminal may require alteration sothat these elements will cooperate with the cor- "responding elements oftheadjacent rel y sta tions. '7 V My invention is capable ofmodificationin 'many ways to suit practical requirements, as may be foundadvantageous in-radio relay-systems. =;Such rnodifications will, ofcourse, be understood to be comprehended within the scope of theinvention.

I claim:

1. The method of utilizing a minimum number of carrier frequencyassignments to the transmitters situated at terminal and repeaterstations of a communications network, while avoiding mutual interferencebetween adjacent links of said network, said method comprising the stepsof allocating at least three different carriers individually to each ofthe single transmitters at one terminal station and at two stationsnearest and next in order in said network, tuning each of two radioreceivers at each repeater station so that reception may be had fromeither of two stations directlyassociated therewith, and connecting eachrepeater station transmitter exclusively to a selected one of thereceivers of the same repeater station, thereby to repeat thetransmission of terminal station, the

- station,

peater stations ltions, the combination of a receiver and peaterstation, each of ,carrier frequency assignments of one of three assignedthe transmitter at I and switching means ,sponsive. to an incomingsignal to cause each repeater station transmitter to be connected to the,frequency B is assigned toa repeater station with in the transmissionrange of said one terminal station, frequency 0 is assigned to the nextrepeaterstation in the direction of the other terminal station andfrequency assignments A, B and-C are: applied progressively to otherrepeater stations situated in the direction of said other transmitterfrequency assignment of said other terminal station being different fromthat of the two repeater stations nearest thereto, means for causing thetransmission range of each of said stations to be ineffective beyondtwice, the distance to each related a pair of receivers at each repeaterstation individually tuned to one and the other of the two saidfrequencies which are exclusive of the transmitter frequency at the samerepeater station, and means automatically operative for modulating eachrepeater station transmitter under the exclusive control of incomingsignals accepted by whichever one of the two associated receiversproduces the first response after a nosignalling period.-

3. In a radio relay system comprising two terminal stations and aplurality of intervening refor interlinking a one-way channel in eitherdirection between said terminal staa transstation, the combinationtransmitter at each resaid transmitters having mitter at each terminalof. two receivers and a predetermined frequencies assigned progressivelyto said stations along said system from one to the other terminalstation, means to cause the transmission range of said stations to beineffective beyond twice the distance ,the receivers at each repeaterstation being indi- ;vidually tuned to three frequencies exclusiverequency at the same repeater station, the re- ,ceiver at each to eachrelated station,

one and the other of two of said of the transmitter terminal stationbeing responsive three frequencies other than that that terminalstation, at each repeater station reto one of said receiver whichaccepts said incoming signal to relay the same, and further switchingmeans at each repeater station to isolate said transmitter from controlby the other receiver thereat.

4. In a radio relay network comprising two terminal stations and aplurality of interveningrepeater stations, transmitting and receivingapparatus at each station, each transmitting apparatus having itscarrier frequency assignment selected from three predeterminedfrequencies assigned progressively to stations from one terminal stationto the other, means for causing the transmission range of each of saidtransmitters to be ineffective beyond the distance between alternaterelated stations to avoid feedback interference with other stations ofsaid network hav- 7 ing the same carrier frequency assignment, the

' receivers at each repeater station being individually tuned to one andthe other of the two of said three frequencies which are exclusive ofthe transmitter frequency at the same repeater station, and means formodulating the outgoing carrier wave ofeach repeater station transmitterby incoming signals of a message to which the receiving apparatus atthat station first responds after a no-signalling period, said signalsbeing borne by a carrier wave of one of said three predeterminedfrequencies, and lock-out means to isolate said transmitting apparatusfrom the mitter frequency assignment of each station being differentfrom that of the two stations nearest thereto and no receiver beingwithin twice the transmission range of any of said transmittersoperating on a frequency to which the receiver is responsive, thereceivers at each repeater station being individually tuned to one and.the other of the two of said three frequencies which are exclusive ofthe transmitter frequency at the same repeater station.

6. A radio relay system including a chain of repeater stations, each ofsaid stations having two receivers and a transmitter, each transmitterbeing tuned to one of three predetermined fref quencies to which onereceiver at each adjacent station is responsive, said three frequenciesbeing assigned progressively to the stations along said chain, thereceivers at each repeater station being individually tuned to one andthe other of the two said frequencies which are exclusive of thetransmitter frequency at the same repeater station, and a terminalstation at each end of the system, each of said terminal stationsincluding a transmitter and a receiver tuned to co-operate "with areceiver and transmitter of the adjacent repeater station, no receiverbeing within the transmission range of a transmitter having the samefrequency assignment and located beyond twice the distance to eachrelated station.

7. A radio relay system including a plurality of repeater stationsinterposed between two termi-.

nal stations, each of said repeater stations having elements comprisingtwo receivers and a transmitter, the carrier frequency assignments ofeach of which element is one of three predetermined frequencies assignedin regular progression to the elements of repeater stations alongsaidsystem from one to the other terminal station, the transmitter frequencyassignment of each station being different from that of the two stationsnearest thereto, means for causing the transmission range of each ofsaid stations to be ineffective beyond twice the distance to eachrelated station, signal responsive means at each repeater station toapply operating potentials to the transmitter, and means to couple themodulating circuit of said transmitter exclusively to the one of theassociated receivers at said station which first responds to signalsafter the lapse of a non-signalling period, and means for locking outthe control of said transmitter by the other of the associatedreceivers.

8. A radio relay system comprising a chain of relay stations, each ofsaid stations having two receivers and a transmitter, each transmitterbeing tuned to one of three predetermined frequencies to which onereceiver at each adjacent station is responsive, means for causing thetransmission range of each of said stations to be ineffective beyondtwice the distance to each related station, the receivers at eachrepeater station individually tuned to one and the other of the two saidfrequencies which are exclusive of the transmitter frequency at the samerepeater station, remote control apparatus in operative association withthe receivers and transmitter at each repeater station, said apparatusincluding switching means responsive to incoming signals to establishexclusive control of the transmitter by whichever one of the twoassociated receivers first responds to said incoming signals, and meansoperative during such response to prevent the reversal of said switchingmeans upon subsequent response of the other receiver to other incomingsignals.

HAROLD H. BEVERAGE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS I Date Number Name 1,624,966 Morris Apr, 19,19271,927,827 Goldsmith Sept. 26, 1933 2,106,806 Latimer et a1 Feb. 1,19382,146,301 Knotts et a1. Feb. 7, 1939 2,155,821 Goldsmith Apr. 25, 19392,250,950 Goldsmith July 29, 1941 2,292,222 Haigis Aug. 4, 1942

